1. Field of the Invention:
This invention relates to an apparatus for manufacturing polyurethane foam slabs in a batch and, in particular, an apparatus for manufacturing them in a continuous fashion.
2. Description of the Prior Art:
Polyurethane foam slabs are usually of a large-sized block type and are cut into slices of a desired thickness or configuration. Conventionally, such slices have found a wider application to an interior design and cushioning material for vehicles.
In the most common method, slabs around 30 to 40 m in length have been manufactured by continuously discharging a polyurethane foam feed solution into a recessed conveyor belt and expanding it therein. This method has a greater advantage of assuring a higher production efficiency.
A batch-type manufacturing method has also partly been adopted which introduces a foam feed solution into a large-sized tank where it is expanded and raised. This method is inferior to the aforementioned continuous method with respect to its reproductivity and, in addition, can be implemented at a relatively narrow location. According to the method, slabs of a desired size can be manufactured by using a foam tank of a corresponding size. For a cylindrical slab a long sheet can effectively been obtained by peeling off or slicing the cylindrical slab, while the latter is rotated.
These known methods have, however, the following disadvantages:
In the continuous manufacturing method using the recessed conveyor belt, a 30 to 60 m production line is needed, requiring a wider spacing and thus a relatively large workshop. Since a slab of a substantially rectangular cross-section is obtained according to this method, a slicing machine has to be reciprocated many times to obtain a sheet of a desired thickness. It is, therefore, difficult to improve a quantity production in high yield. Furthermore, the slab which is substantially rectangular in cross-section is irregularly formed at its top face and has a rough surface and a hardened layer. It is, therefore, necessary to cut off the top surface portion of the slab a few centimeters from its top face, offering a material loss problem.
Indeed, the conventional batch type method has the advantage of requiring a bulky apparatus and a larger installation spacing, but it is far inferior to the continuous method with respect to its productivity, thus posing a critical problem.